We perform 2D DNS in a broad \(Ra\) -range, \(10^7\le Ra\le 10^{10}\) , with fixed aspect ratio \(\Gamma = 2\) .
\(Pr\)  is fixed to \(11.57\)  in all simulations, which corresponds to the value for water at \(4^\circ \rm {C}\) .
In addition, we perform 3D DNS for \(Ra=10^7\)  and \(\Gamma =4\) .
The governing equations are solved with the second-order finite-difference code AFiD [1]}, [2]}, which has already been extensively used to study RBC, see, e.g., [3]}, [4]}.
The used staggered grids satisfy the resolution requirements for DNS [5]}.
Details on the simulations can be found in the Supplementary materials.
